1. Field of the Invention
The present invention relates generally to the field of construction apparatus and more particularly, but not by way of limitation, to a planer type road construction apparatus affording precision planing of an existing paved roadway.
2. Description of the Prior Art
As was discussed in detail in U.S. Pat. No. 4,139,318, maintenance and repair of paved roadways by a planing process provides an economical and energy-conserving alternative to conventional repaving and resurfacing. The planing process, which involves cutting away a selected upper portion of the roadway, permits relative depth reduction of holes, bumps or recesses in the roadway by decreasing the overall thickness of the roadway. Thereafter, the roadway may be repaved to a specified thickness, thereby eliminating wasteful buildup of paving material on the roadway.
The planer apparatus described in U.S. Pat. No. 4,139,318 has provided a maneuverable, fast-moving and highly accurate improvement over prior art devices for accomplishing roadway planing operations. By virtue of the automatic elevation and cross-slope controls featured on the apparatus, the operator need not possess unusual skill or experience in order to plane a roadway surface to a predetermined grade and cross-slope. The dust control and reclaiming features of the apparatus described in the above-mentioned patent permit planing to be undertaken without generation of unrecovered atmospheric dust or pavement debris, thereby affording clean and waste-free planing operation.
While the apparatus described in the abovementioned patent has proven highly suitable for most planing applications, it lacks design features adapting it to use in certain difficult operational environments. For example, the design of the apparatus makes it difficult to achieve close side approaches to vertical obstructions such as walls and curbs. Close side approaches by such prior art apparatus are prevented by bulky chain drive assemblies for powering rotation of the cutter drum, which are normally mounted on either side of the apparatus.
During extremely cold weather conditions, prior art planers have experienced difficulty in achieving adequate dust control, which has been provided by water spray devices used in conjunction with planing cutters. During winter conditions dust control has been hampered by water freezing in the spray nozzles used to spray the dust generated during planing operations.
As with any type of powered machinery, there are occasions of power failure in a planer apparatus which require field or shop repair. In units the size of prior art planing cutters, including that described in U.S. Pat. No. 4,139,318, failure of the power drive unit during field operation results in an immediate immobilization of the apparatus. If this occurs, the apparatus can be moved only by towing, a difficult and time-consuming process. Should a power failure occur while the apparatus is located in a depressed cut in the roadway, it may be extremely difficult and impractical to tow the apparatus from the cut, in which case, the usual procedure is to repair or replace the power drive unit in the field.
During planing operations, it has been found that repair or replacement of the cutting teeth of the cutter drum is required during field operation of the planing apparatus. To achieve this repair or replacement, a cutting bit must be properly positioned so as to permit access by a field mechanic. It has been found that the cutting bit can be properly positioned only by turning the cutter drum by selectively actuating the main power drive unit to turn the cutting drum. Since this turning occurs at the same rapid rate of rotation as that of the cutter drum during planing operations, the cutter drum presents a potential personnel hazard during such repairs unless the main power unit is completely shut off and locked in this mode while personnel are working near the cutter drum. Once work has been completed on the cutting bits accessible in one setting of the cutter drum, the area must be vacated while the main drive unit is again actuated and the proper safety procedures are again invoked. This time consuming but necessary routine renders cutting bit repair or replacement a costly process.
Additionally, difficulties have been experienced with the reclaimer assemblies utilized in prior art planers of the type described in the above mentioned patent during actual operational conditions. Dirt and dust from the material carried by the reclaimer assembly tends to accumulate in and around conveyor rollers in the reclaimer assembly. Further, the conveyor motors of such prior art reclaimers have usually projected from the conveyor frame, making such motors vulnerable to collision damage by trucks positioned below the discharge end of the conveyor.